Google yesterday announced on the Lat Long Blog
that it will begin to offer the opportunity to read and write user
generated reviews of businesses that show up in local listings in
Google Maps.

Reviews in Google Maps can now be found in a small link that
accompanies most business listings. These will join the aggregated
professional reviews that Google has traditionally pulled from various
sources.

The AJAX functionality of the new reviews feature causes a small
window to open in which users can easily write a review and designate a
rating from one to five stars. Though Google is showing up late to the
user reviews party (Yahoo! has had this for almost two years), this
feature is decidedly simpler and more intuitive than writing reviews in
Yelp, Yahoo! and others.